fuel cell module

Abstract

To alleviate an excessive pressure rise when modified water is vaporized, thereby stabilizing gas flow rate.SOLUTION: A fuel cell module includes: a fuel cell that generates electricity based on an anode gas and a cathode gas; a vaporization section that introduces modified water to produce steam; a reforming section that introduces a raw fuel gas as well as steam that is led out from the vaporization section to produce the anode gas by steam reforming; and a combustion section that heats the vaporization section and the reforming section by combustion heat. The vaporization section has a double tube structure in which a modified water introduction pipe for introducing modified water is used as an inner pipe and a steam lead-out pipe for leading out steam is used as an outer pipe.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell modules. [Background technology]

[0002] Conventionally, a fuel cell module has been proposed that includes a fuel cell that generates electricity based on anode gas and cathode gas, a vaporization section (evaporation section) that vaporizes reforming water supplied from a reforming water supply pipe to generate steam, and a reforming section that steam-reforms reforming material supplied from a raw material supply pipe to generate anode gas. For example, Patent Document 1 discloses a fuel cell module in which the vaporization section and the reforming section are housed in a housing and communicate with each other, and a raw material reforming supply pipe and a reforming water supply pipe are configured in a double-pipe structure at one end of the housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6477085 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described fuel cell module, if more water vapor than expected is generated in the vaporizer, the pressure on the supply side of the reformer may rise, making it impossible to supply a sufficient amount of raw material from the raw material supply pipe, which may result in a shortage of anode gas supplied to the fuel cell and adversely affect the fuel cell module.

[0005] The main object of the present disclosure is to alleviate excessive pressure rise that occurs when reforming water is vaporized, thereby stabilizing the gas flow rate. [Means for solving the problem]

[0006] The present disclosure has adopted the following means to achieve the above-mentioned main object.

[0007] The fuel cell module of the present disclosure comprises: a fuel cell that generates electricity based on the anode gas and the cathode gas; a vaporization section that introduces reforming water to generate steam; a reforming section that introduces the raw fuel gas and the steam derived from the vaporizing section and generates the anode gas by steam reforming; a combustion unit that heats the vaporization unit and the reforming unit with combustion heat; Equipped with The vaporization section has a double-pipe structure in which a reforming water inlet pipe for introducing reforming water is an inner pipe and a steam outlet pipe for guiding steam is an outer pipe. The gist of this is as follows.

[0008] In the fuel cell module of the present disclosure, the vaporization unit has a double-pipe structure with a reforming water inlet pipe as an inner pipe for introducing reforming water and a steam outlet pipe as an outer pipe for discharging steam. This allows the steam to be discharged through an annular gap (steam outlet pipe) on the outside of the double-pipe structure, thereby increasing pressure loss. This reduces the amount of steam discharged through the steam outlet pipe, even if more steam than expected is generated in the vaporization unit, thereby mitigating excessive pressure increases on the raw fuel gas inlet side to the reforming unit. This allows the raw fuel gas and steam to be stably introduced into the reforming unit, stabilizing the anode gas flow rate.

[0009] The fuel cell module of the present disclosure may include a cylindrical section that forms a cylindrical closed space to accommodate the vaporization section and the reforming section, the vaporization section having the double-pipe structure such that the reforming water inlet pipe penetrates one end wall of the cylindrical section and the steam outlet pipe opens just before the end wall, the cylindrical section having a raw fuel gas inlet pipe that penetrates the end wall and introduces a raw fuel gas, and a mixing space that mixes the steam discharged from the steam outlet pipe and the raw fuel gas introduced from the raw fuel gas inlet pipe and introduces the mixed gas to the reforming section. This allows the steam and raw fuel gas to be appropriately mixed before being introduced to the reforming section, thereby making it possible to more stabilize the flow rate of the anode gas.

[0010] In the fuel cell module of the present disclosure, the combustion section may have a combustion device that ignites and burns offgas introduced from the fuel cell, the tubular section may be formed to surround the combustion section with a predetermined gap between it and the combustion device so that the combustion device is located on the opposite side of the one end wall, the vaporization section may be disposed inside the combustion section, and the reforming section may be disposed in the predetermined gap. This allows for a compact configuration in which the vaporization section, reforming section, and combustion section are housed in the tubular section. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a fuel cell module 10. FIG. [Figure 2] FIG. 2 is a schematic diagram of a reforming unit 20. [Figure 3] 3 is a cross-sectional view taken along the line AA in FIG. 2. [Figure 4] 3 is a cross-sectional view of FIG. 2 taken along line B-B. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic diagram of a fuel cell module 10. As shown in FIG. 1, the fuel cell module 10 of this embodiment includes a fuel cell stack 11 that generates electricity through an electrochemical reaction between hydrogen in an anode gas and oxygen in a cathode gas, a reforming unit 20 that generates anode gas by reforming a raw fuel gas (e.g., natural gas or LP gas) by steam reforming, first and second heat exchangers 41, 42, and a condenser 50. The fuel cell stack 11, the reforming unit 20, and the first and second heat exchangers 41, 42 are housed in a thermally insulating, box-shaped module case 12. The fuel cell module 10, together with a raw fuel gas supply device, a reforming water supply device, an air supply device, and a hot water storage tank (not shown), constitute a fuel cell system. The raw fuel gas supply device supplies raw fuel gas to the reforming unit 20 (reforming section 22), the reforming water supply device supplies reforming water required for reforming (steam reforming) raw fuel gas into anode gas to the reforming unit 20 (evaporation section 21), and the air supply device supplies air as cathode gas to the fuel cell stack 11. The hot water storage tank recovers heat generated in the fuel cell module 10 and stores it in hot water.

[0013] The fuel cell stack 11 comprises multiple solid oxide type unit cells arranged vertically, each having an electrolyte such as zirconium oxide and an anode electrode and a cathode electrode sandwiching the electrolyte. An anode gas passage is formed in the anode electrode of each unit cell. A cathode gas passage is also formed in the cathode electrode of each unit cell.

[0014] 1 and 2, the reforming unit 20 has a vaporization section 21, a reforming section 22, a combustion section 23, and a pressure equalization section 24 (see FIG. 2). As shown in FIG. 2, these are covered by an outer tube 25 that is cylindrical and has closed ends in the axial direction.

[0015] A reforming water pipe 32 of a reforming water supply device is connected to the vaporization section 21, and reforming water is introduced through the reforming water pipe 32. The vaporization section 21 heats the introduced reforming water with heat (combustion heat) from the combustion section 23, and evaporates the reforming water to generate steam. The steam generated by the vaporization section 21 is mixed with the raw fuel gas introduced into the pressure equalization section 24 in the pressure equalization section 24, and the mixed gas flows into the reforming section 22.

[0016] The reforming unit 22 has a Ru-based or Ni-based reforming catalyst 221 (see FIG. 2) filled therein, and generates hydrogen gas and carbon monoxide through a reaction (steam reforming reaction) of the mixed gas by the reforming catalyst 221 in the presence of heat from the combustion unit 23. The reforming unit 22 further generates hydrogen gas and carbon dioxide through a reaction (carbon monoxide shift reaction) between the carbon monoxide generated in the steam reforming reaction and steam. As a result, the reforming unit 22 generates anode gas containing hydrogen, carbon monoxide, carbon dioxide, steam, unreformed raw fuel gas, etc. The anode gas generated by the reforming unit 22 flows through the anode gas piping 33 into the anode gas passage of each unit cell of the fuel cell stack 11 and is supplied to the anode electrode.

[0017] Air as a cathode gas flows from an air supply device through a cathode gas pipe 34 into the cathode gas passage of each unit cell of the fuel cell stack 11 and is supplied to the cathode electrode. At the cathode electrode of each unit cell, oxide ions (O 2- ) is generated, and the oxide ions pass through the electrolyte and react with hydrogen and carbon monoxide at the anode electrode to generate electrical energy. The output terminal of the fuel cell stack 11 is connected to the input terminal of a power conditioner (not shown), and the power generated by the fuel cell stack 11 is converted to AC power by the power conditioner and supplied to an electrical load.

[0018] Anode gas (hereinafter referred to as "anode off-gas") that is not used in the electrochemical reaction (power generation) in each unit cell is temporarily guided outside the module case 12 through the anode off-gas piping 35 and supplied to a condenser 50 (cooler) installed outside the module case 12. The anode off-gas supplied to the condenser 50 is cooled by heat exchange with hot water from a hot water storage tank, and the water vapor contained in the anode off-gas is removed. The anode off-gas is then reintroduced into the module case 12 and supplied to the combustion section 23 of the reforming unit 20. The water obtained by condensing the water vapor contained in the anode off-gas is stored in a reforming water tank and used as reforming water.

[0019] Furthermore, the cathode gas (hereinafter referred to as "cathode off-gas") that has not been used in the electrochemical reaction (power generation) in each unit cell is supplied to the combustion section through a cathode off-gas pipe .

[0020] The anode off-gas that flows into the combustion section 23 is a combustible gas containing fuel components such as hydrogen and carbon monoxide, and is mixed with the cathode off-gas that flows into the combustion section 23 and contains oxygen. When the mixed gas (hereinafter referred to as "off-gas") is ignited in the combustion section 23 by a burner device 235 that includes an ignition device, the combustion of the off-gas generates heat necessary for generating steam in the vaporization section 21 and for the steam reforming reaction in the reforming section 22. The combustion section 23 also generates combustion exhaust gas containing unburned fuel, which passes through the combustion exhaust gas piping 37 and the combustion catalyst before being discharged into the outside air. The combustion catalyst is an oxidation catalyst for re-burning the unburned fuel in the combustion exhaust gas.

[0021] The first and second heat exchangers 41, 42 are both installed inside the module case 12. The first heat exchanger 41 exchanges heat between the anode offgas flowing upstream of the condenser 50 in the anode offgas piping 35 and the anode offgas flowing downstream of the condenser 50 in the anode offgas piping 35. The second heat exchanger 42 exchanges heat between the combustion exhaust gas flowing through the combustion exhaust gas piping 37 and the cathode gas flowing through the cathode gas piping 34.

[0022] 2, the combustion section 23 of the reforming unit 20 has a cylindrical combustion chamber 231 whose both ends in the cylindrical axis direction are closed by end walls 232, 233, and a burner device 235 provided on the inner surface side of the end wall 232 of the combustion chamber 231. An anode offgas pipe 35 is connected to the end wall 232 of the combustion chamber 231 so that anode offgas flows into the combustion chamber 231 from inside the burner device 235, and a cathode offgas pipe 36 is connected to the end wall 232 of the combustion chamber 231 so that cathode offgas flows into the combustion chamber 231 from outside the burner device 235. In addition, a combustion exhaust gas pipe 37 is connected to the end wall 233 of the combustion chamber 231 opposite the end wall 232 so that combustion exhaust gas generated by combustion of the anode offgas and cathode offgas in the combustion chamber 231 flows out of the unit.

[0023] The vaporizer 21 is disposed inside the combustion chamber 231 so as to be adjacent to, and spaced a predetermined distance from, the end wall 233 of the combustion chamber 231 opposite the end wall 232 on which the burner device 235 is disposed. A reforming water pipe 32 for introducing reforming water is disposed in the end wall 217 of the vaporizer 21 at the end on the same side as the end wall 233 of the combustion chamber 231. The reforming water pipe 32 penetrates the end wall 254 of the outer pipe 25, extends to the outside, and is connected to a reforming water supply device (reforming water pump) not shown. The reforming water pump is configured as, for example, a plunger pump that discharges reforming water by intermittently driving (reciprocating) a plunger using electromagnetic force and spring force, and is configured to intermittently discharge reforming water into the reforming water pipe 32.

[0024] The interior of vaporization section 21 is divided into three sections: dripping section 211, filling section 212, and buffer section 213, by mesh-like partition members 215, 216 such as punched metal having a plurality of communicating holes (through holes). Fig. 3 is a cross-sectional view taken along line AA in Fig. 2, and Fig. 4 is a cross-sectional view taken along line BB in Fig. 2. In this embodiment, dripping section 211 and filling section 212, which is separated from dripping section 211 by partition member 215, are provided on the end wall 217 side, and buffer section 213, which is separated from dripping section 211 and filling section 212 by partition member 216, is provided on the end wall 218 side opposite end wall 217.

[0025] The drip section 211 is a space into which the reforming water introduced through the reforming water pipe 32 drips. The filling section 212 is a space filled with, for example, alumina spheres 212a as a spherical heat storage member with high thermal conductivity, and the alumina spheres 212a are heated by the heat of combustion generated in the combustion chamber 231. The reforming water that drips into the drip section 211 can flow into the filling section 212 through the communication holes in the partition member 215. The water that flows into the filling section 212 is vaporized while being diffused in the gaps between the filled alumina spheres 212a. The drip section 211 and the buffer section 213 are not filled with alumina spheres 212a. When water accumulates on the bottom surface of the filling section 212, it flows into the buffer section 213 through the holes in the partition member 216 and is vaporized in the buffer section 213. The buffer section 213 is provided on the end wall 218 side, i.e., on the side closer to the burner device 235, and therefore has a higher temperature than the drip section 211 and the packed section 212. Therefore, the evaporation of the water that flows into the buffer section 213 is promoted.

[0026] The buffer section 213 is a space that is at least larger than the drip section 211 and the filling section 212, and in this embodiment, is larger than the combined space of the drip section 211 and the filling section 212, for example, it is partitioned to be a space that is about 10 times the size of the filling section 212. Therefore, in the vaporization section 21, the buffer section 213 can sufficiently absorb the volume expansion that occurs when the reforming water vaporizes into steam. This suppresses fluctuations in the pressure of the steam that is drawn out from the vaporization section 21, and allows the raw fuel gas and steam to be stably introduced into the reforming section 22, thereby stabilizing the gas flow rate of the anode gas.

[0027] Furthermore, a steam pipe 214 for delivering vaporized steam is connected to the end wall 217 of the vaporization section 21 at the same end as the end wall 233 of the combustion chamber 231, i.e., to the end walls 217, 233 on which the reforming water pipe 32 is arranged. The vaporization section 21 of this embodiment has a double-pipe structure in which the reforming water pipe 32 is the inner pipe and the steam pipe 214 is the outer pipe. The reforming water pipe 32 penetrates the end wall 254 of the outer pipe 25 and extends to the outside, but the steam pipe 214 is formed to a length that opens into the pressure equalizing section 24 before the end wall 254 of the outer pipe 25. Therefore, the water vapor vaporized in the filling section 212 or the buffer section 213 is delivered from the dripping section 211 through the steam pipe 214 to the pressure equalizing section 24 and is supplied to the reforming section 22 via the pressure equalizing section 24. Since the steam pipe 214 and the reforming water pipe 32 have a double pipe structure, the steam passes through an annular gap and is led to the pressure equalizing section 24. Therefore, even if the steam pipe 214 is formed to have a short length, the pressure loss can be made relatively large.

[0028] The reforming section 22 has a reforming catalyst 221 arranged in a cylindrical space (cylindrical space, a predetermined gap) formed between the outer peripheral surface of the side wall (circumferential wall) 234 of the combustion chamber 231 and the inner peripheral surface of the side wall (circumferential wall) 251 of the outer tube 25. Steam and raw fuel gas flow into the reforming section 22 from one end in the cylindrical axis direction of the cylindrical space, and anode gas generated by steam reforming flows out from the other end in the cylindrical axis direction. The anode gas flowing out of the reforming section 22 is supplied to the anode electrode of the fuel cell stack 11 through an anode gas pipe 33.

[0029] The pressure equalizing section 24 has a space defined by the end wall 233 of the combustion chamber 231 and the end wall 254 of the outer pipe 25. The reforming water pipe 32 and the combustion exhaust gas pipe 37 described above are attached to the end wall 254 of the outer pipe 25 so as to penetrate the pressure equalizing section 24, and the raw fuel gas pipe 31 is connected so that the raw fuel gas flows into the pressure equalizing section 24. The space of the pressure equalizing section 24 also communicates with the inside of the vaporizing section 21 via the steam pipe 214. As a result, the raw fuel gas and steam flow into the reforming section 22 through the pressure equalizing section 24, and the pressure equalizing section 24 functions as a buffer section, enabling the raw fuel gas and steam to be supplied approximately uniformly in the circumferential direction to the cylindrical space (reforming catalyst 221) of the reforming section 22. Furthermore, due to the above-described double pipe structure, even if more water vapor than expected is generated in the vaporization section 21, the amount of water vapor led from the vaporization section 21 to the pressure equalization section 24 can be reduced, thereby mitigating an excessive increase in pressure in the pressure equalization section 24. This prevents a pressure increase in the pressure equalization section 24 from interfering with the supply of raw fuel gas to the reforming section 22, and allows the raw fuel gas and water vapor to be appropriately supplied to the reforming section 22, thereby stabilizing the gas flow rate of the anode gas.

[0030] In the fuel cell module 10 of the present embodiment described above, the vaporizer 21 has a double-pipe structure with the reforming water pipe 32 as the inner pipe and the steam pipe 214 as the outer pipe. Steam is discharged through the outer annular gap (steam pipe 214) of the double-pipe structure, thereby increasing pressure loss. Therefore, even if the vaporizer 21 generates more steam than expected, the amount of steam discharged can be reduced, mitigating excessive pressure buildup on the raw fuel gas introduction side to the reformer 22. This allows the raw fuel gas and steam to be stably introduced into the reformer 22, stabilizing the anode gas flow rate. This prevents damage to the fuel cell stack 11 due to oxidation and expansion of the anode electrode, which would otherwise occur if the flow rate of the anode gas flowing to the fuel cell stack 11 were insufficient. Furthermore, it prevents misfires due to an insufficient flow rate of the anode off-gas flowing to the combustor 23.

[0031] Furthermore, the vaporization section 21 has a double-pipe structure in which the reforming water pipe 32 penetrates the end wall 254 of the outer pipe 25, and the steam pipe 214 opens just before the end wall 254. The outer pipe 25 is provided with the raw fuel gas pipe 31 that penetrates the end wall 254, and is also formed with a pressure equalization section 24 that mixes the steam delivered from the steam pipe 214 with the raw fuel gas introduced from the raw fuel gas pipe 31 and introduces the resulting mixture to the reforming section 22. This allows the steam and raw fuel gas to be appropriately mixed before being introduced into the reforming section 22, thereby making it possible to further stabilize the flow rate of the anode gas.

[0032] Moreover, the vaporizing section 21, the reforming section 22, and the combustion section 23 can be housed in the outer tube 25, resulting in a compact configuration.

[0033] In the above-described embodiment, the vaporization section 21, the reforming section 22, and the combustion section 23 are housed in the outer tube 25 in one unit (reforming unit 20), but the present invention is not limited to this. For example, the vaporization section 21 and the reforming section 22 may be one unit, and the combustion section 23 may be a separate unit.

[0034] In the above-described embodiment, the vaporizer 21 has the dripping section 211 formed separately from the filling section 212 and the buffer section 213, but this is not limiting, and the dripping section 211 may be included in the filling section 212. That is, it is sufficient that the interior of the vaporizer 21 is partitioned into the filling section 212 and the buffer section 213. Alternatively, the interior of the vaporizer 21 may not be partitioned into the filling section 212 and the buffer section 213, but may be a single space (filling section 212).

[0035] In the above-described embodiment, the vaporization section 21 is arranged inside the combustion section 23 (combustion chamber 231), and the buffer section 213 is on the burner device 235 side, but this is not limiting. For example, the arrangement direction of the filling section 212 and the buffer section 213 may be set to a direction perpendicular to the cylindrical axis direction of the outer tube 25, so that only the buffer section 213 is not on the burner device 235 side. Also, a configuration in which the vaporization section 21 is not arranged inside the combustion section 23 (combustion chamber 231) may be used.

[0036] In the above-described embodiment, the anode off-gas from the fuel cell stack 11 is supplied to the condenser 50, where water vapor contained in the anode off-gas is removed, and the anode off-gas is then supplied to the combustion section 23. However, the anode off-gas from the fuel cell stack 11 may be supplied directly to the combustion section 23. In this case, the combustion exhaust gas generated by combustion of the off-gas in the combustion section 23 may be supplied to the condenser, and the water vapor contained in the combustion exhaust gas may be condensed.

[0037] The correspondence between the main elements of the embodiment and the main elements of the present disclosure described in the "Means for Solving the Problems" section will be explained. The fuel cell stack 21 of the embodiment corresponds to the "fuel cell" of the present disclosure, the vaporization section 21 corresponds to the "vaporization section," the reforming section 22 corresponds to the "reforming section," the combustion section 23 corresponds to the "combustion section," the reforming water pipe 32 corresponds to the "reforming water introduction pipe," and the steam pipe 214 corresponds to the "steam discharge pipe." The outer pipe 25 corresponds to the "cylindrical section," the raw fuel gas pipe 31 corresponds to the "raw fuel gas introduction pipe," and the pressure equalization section 24 corresponds to the "mixing space." The burner device 235 corresponds to the "combustion device."

[0038] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0039] The above describes the form for carrying out the present invention using an embodiment, but the present invention is not limited to such an embodiment in any way, and it goes without saying that the present invention can be carried out in various forms within the scope that does not deviate from the gist of the present invention. [Industrial Applicability]

[0040] The present invention can be used in the fuel cell module manufacturing industry and the like. [Explanation of symbols]

[0041] 10 fuel cell module, 11 fuel cell stack, 12 module case, 20 reforming unit, 21 vaporization section, 22 reforming section, 23 combustion section, 24 pressure equalization section, 25 outer pipe, 31 raw fuel gas piping, 32 reforming water piping, 33 anode gas piping, 34 cathode gas piping, 35 anode off-gas piping, 36 cathode off-gas piping, 37 combustion exhaust gas piping, 41 first heat exchanger, 42 second heat exchanger, 50 condenser, 51 temperature sensor, 211 dripping section, 212 filling section, 212a alumina spheres, 213 buffer section, 214 water vapor piping, 215, 216 partition members, 217, 218 end walls, 221 reforming catalyst, 231 combustion chamber, 232, 233 end walls, 234 peripheral wall, 235 burner apparatus, 251 side walls, 254 end walls;

Claims

1. a fuel cell that generates electricity based on the anode gas and the cathode gas; a vaporization section that introduces reforming water to generate steam; a reforming section that introduces the raw fuel gas and the steam derived from the vaporizing section and generates the anode gas by steam reforming; a combustion unit that heats the vaporization unit and the reforming unit with combustion heat; Equipped with The vaporization section has a double-pipe structure in which a reforming water inlet pipe for introducing reforming water is an inner pipe and a steam outlet pipe for guiding steam is an outer pipe. Fuel cell module.

2. 10. The fuel cell module of claim 1, a cylindrical portion that forms a cylindrical closed space to accommodate the vaporizing portion and the reforming portion; the vaporization section has a double-pipe structure in which the reforming water inlet pipe penetrates one end wall of the cylindrical section and the water vapor outlet pipe opens just before the end wall, The cylindrical portion is provided with a raw fuel gas inlet pipe that penetrates the end wall and introduces raw fuel gas, and a mixing space is formed in which steam discharged from the steam discharge pipe and raw fuel gas introduced from the raw fuel gas inlet pipe are mixed and introduced to the reforming portion. Fuel cell module.

3. 3. The fuel cell module according to claim 2, the combustion unit has a combustion device that ignites and burns the off-gas introduced from the fuel cell, the cylindrical portion is formed to surround the combustion portion with a predetermined gap therebetween, so that the combustion device is located on the opposite side of the one end wall, the vaporization section is disposed inside the combustion section, The modified portion is disposed in the predetermined gap. Fuel cell module.

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